import java.util.Scanner;

public class test4 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long n = in.nextLong();
        //先开平方然后四舍五入
        double flag = Math.sqrt(n);
        n = Math.round(flag);
        System.out.println(n*n);
    }
}
